#include "UnityPrefix.h"
#include "PerlinNoise.h"

inline static float fade(float t) { return t * t * t * (t * (t * 6 - 15) + 10); }
inline static float lerp(float t, float a, float b) { return a + t * (b - a); }
inline static float grad(int hash, float x, float y, float z) {
	int h = hash & 15;                      // CONVERT LO 4 BITS OF HASH CODE
	float u = h<8 ? x : y,                 // INTO 12 GRADIENT DIRECTIONS.
	v = h<4 ? y : h==12||h==14 ? x : z;
	return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
}

inline static float grad2(int hash, float x, float y) {
	int h = hash & 15;                      // CONVERT LO 4 BITS OF HASH CODE
	float u = h < 8 ? x : y,                 // INTO 12 GRADIENT DIRECTIONS.
	v = h < 4 ? y : h==12 || h==14 ? x : 0;
	return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
}

static int p[] = 
{ 
	151,160,137,91,90,15,
	131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
	190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
	88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
	77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
	102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
	135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
	5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
	223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
	129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
	251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
	49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
	138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180,
	151,160,137,91,90,15,
	131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
	190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
	88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
	77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
	102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
	135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
	5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
	223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
	129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
	251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
	49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
	138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
};



float PerlinNoise::Noise(float x, float y) {
	x = Abs(x);
	y = Abs(y);

	int floorX = int(x);
	int floorY = int(y);
	
	int X = floorX & 255;                  // FIND UNIT CUBE THAT
	int Y = floorY & 255;                  // CONTAINS POINT.
	x -= floorX;                                // FIND RELATIVE X,Y,Z
	y -= floorY;                                // OF POINT IN CUBE.
	float u = fade(std::min(x, 1.0f));          // COMPUTE FADE CURVES
	float v = fade(std::min(y, 1.0f));          // FOR EACH OF X,Y,Z.
	int A = p[X  ]+Y, AA = p[A], AB = p[A+1],      // HASH COORDINATES OF
	B = p[X+1]+Y, BA = p[B], BB = p[B+1];      // THE 8 CUBE CORNERS,
	
	float res = lerp(v, lerp(u, grad2(p[AA  ], x  , y   ),  // AND ADD
				 grad2(p[BA  ], x-1, y )), // BLENDED
			 lerp(u, grad2(p[AB  ], x  , y-1 ),  // RESULTS
				 grad2(p[BB  ], x-1, y-1 )));// FROM  8
	 return res;
}
